identification of metrics for measuring system attributes, e.g. to determine
when a system is nearing the limits of its processing/memory capacity

When can a performance investigation take
place?

Performance can be investigated at every stage of the development cycle, but
the type of investigation will vary, some of the most likely investigations
are:

Before design: Performance focused architecture design and performance
experiments.During design: Performance prediction to validate the design.During build: Prediction to validate the design and focus resources.After build: Prediction and testing to discover areas of concern.During testing: Performance testing and optimisation to check for system
load and response times and to improve them as needed.After delivery: Performance testing to check system load and to warn
when the system nears the end of its useful life. Performance optimisation
to keep a system useful for longer.

When is a performance investigation worthwhile?

Performance investigations bring the best results when one or more of the following
apply:

There are a large number of user accesses to the site.

There is a large data set.

There is strong security in place.

Each user accesses the system frequently.

The system is used internationally.

There can be a sudden increase in use.

A large amount of data is returned.

The current system response time is too slow.

The current system is overloaded.

If several of the above factors apply, then the risk of a system failing to
meet the performance requirements is high and a performance investigation can
reduce the risk greatly.